Abstract/Summary Obesity increases morbidity risks for several chronic metabolic disorders including diabetes and cardiovascular disease, and has been linked to both systemic and white adipose tissue inflammation. Brown adipose tissue (BAT), a fat tissue which protects against hypothermia, represents a novel target to reduce obesity-associated metabolic disorders. The goal of this proposal is to test whether dietary omega-3 fatty acids (namely eicosapentaenoic acid, EPA) with known anti-inflammatory effects potentially reduce high fat associated adiposity and metabolic alterations via activation of brown fat. We previously demonstrated that EPA-enriched high-fat diets significantly reduced diet-induced obesity, insulin resistance, and inflammation to levels comparable to those in low-fat-fed mice. Furthermore, our recent preliminary data show that these EPA-fed mice also manifest significantly higher brown fat UCP1 protein levels (i.e., uncoupling protein, a BAT-specific thermogenic marker) along with significant increases in gene expression for other markers of thermogenesis. Given the emerging role of BAT in human studies, it is critical to understand how bioactive dietary components such as EPA activate BAT. We hypothesize that the beneficial metabolic effects of EPA in obesity are in part mediated through increasing BAT thermogenic capacity (via upregulation of UCP1) and induction of master regulators of thermogenesis. This hypothesis will be tested in two specific aims through a series of integrated cellular, molecular and physiological studies using mouse models, cultured adipocytes (white and brown) and human mesenchymal stem cells. In aim 1 we will determine in vivo the mechanisms mediating beneficial effects of EPA in BAT and other depots in high-fat-fed wild type and UCP1 knockout mice. In aim 2, using white and brown adipose stem cells derived from animals in aim 1, and human mesenchymal stem cells treated with EPA, we will further dissect the molecular mechanisms by which EPA activates BAT and thermogenic markers (such as UCP1 and PGC1alpha). One of the major outcomes of this research is to provide science-based evidence for potential use of omega-3 fatty acids for improving metabolic health and possibly preventing and/or treating obesity. In addition, we will elucidate mechanisms mediating activation of brown fat by a safe dietary intervention with other proven health benefits. Our studies are consistent with the NIH Strategic Plan for Obesity Research and NCCIH mission emphasizing science-based information to support the usefulness and safety of complementary and integrative health interventions to improve health and health care. The proposed studies are highly innovative and are expected to impact obesity treatment and prevention strategies.